(135c) Water (resource) Conservation Using Closed-Loop, Evaporative Cooling Systems for Process, Power, and Refining Applications

Almost every large plant is evaluating how to use less (fresh) water or are unable to acquire additional water for cooling. Many are also constrained by zero discharge restrictions.

Consequently, water availability and water quality are becoming increasingly important considerations in facility design and operation. Closed-loop, evaporative cooling is a cost-effective heat transfer technology that also optimizes use of scarce water resources.

Systems such as Wet Surface Air Coolers are used in a wide variety of process, chemical and industrial facilities for fluid cooling and vapor condensing.

These units combine a heat exchanger and cooling tower in a single structure, cooling the process stream by evaporative heat transfer.

These are several important features of the WSAC including providing lower outlet temperature and being able to use poor quality water as makeup. Water resources can be blowdown from other equipment, effluent from sewage treatment facilities, gray water, storm water collection, agricultural runoff and produced water from mining and drilling processes.

Units can be manufactured with a wide variety of materials depending on water quality, water treatment and cycles of concentration.

The WSAC is also used for adding capacity in ?thermally challenged? plants. This allows for additional direct cooling without having to acquire additional makeup water.

For water-limited applications (when not enough water is available for cooling the entire load), a hybrid unit incorporating a dry and wet section can be used.

Water (resource) issues will continue to have an increased impact on plant design and operation. Closed-loop, evaporative coolers can help maintain plant performance while utilizing water streams that are currently unusable with conventional towers and heat exchangers. This paper will also include a comparison to other alternative technologies, materials of construction, water treatment and specific case studies.